1. Field of the Invention
The present invention relates to an image forming material that is advantageously used for an image formation by the use of a transferring process, such as a production of a color filter to be used for a manufacturing process of a color liquid-crystal display and the like.
2. Description of the Related Art
An image forming material, which is used for forming a photosensitive resin layer on a substrate serving as a body to be transferred, by transferring the photosensitive resin layer formed on a support onto the substrate, has been well known by, for example, Japanese Patent Application Publication (JP-B) No. 56-40824. This image forming material is used for manufacturing products such as printed circuits, intaglio/letterpress printing plates, name plates, multi-color trial print samples, offset printing plates and screen printing stenciles. The above-mentioned image forming material is normally constituted by a support, an intermediate layer (separation layer), optionally a thermoplastic resin layer, and a photosensitive resin layer. And in the case when an image is formed on the transferred body, the surface of the photosensitive resin layer of the image forming material is made in close-contact with the substrate serving as the body to be transferred. And after only the support has been separated therefrom, the transferred body is exposed through the intermediate layer, and further subjected to a developing process so that the image is formed on the substrate. In this case, the above-mentioned intermediate layer has a function for blocking oxygen, and is advantageously used for exposure in the air. Since its film is thin as having the thickness of 0.5 to 5 μm so that no adverse effects are particularly caused with respect to resolution. Moreover, the above-mentioned thermoplastic resin layer is allowed to absorb irregularities on the undercoat layer (that is, irregularities caused by the image that has been already formed).
For example, in general, a color filter, which is used for a color liquid crystal display and the like, has a basic structure in which respective pixels of R, G and B (red, green, blue) are formed and black matrixes (K) are formed between the gaps thereof so as to improve the display contrast and the like. The surfaces of these respective pixels of R, G and B and K in the color filter are required to have high smoothness. In other words, when an image is formed on the color-filter-use substrate surface by transferring a photosensitive resin layer thereon by the use of the above-mentioned image forming material, color irregularities tend to occur in the pixels unless not only the photosensitive resin layer, but also thermoplastic resin layer has superior smoothness (that is, when there are irregularities in the film thickness). In the case when a color liquid crystal display is manufactured by using such a color filter having color irregularities, with respect to pixels obtained for use in the color liquid crystal display, a coating process needs to be carried out in a manner so as not to cause coating irregularities and cissing during the coating process, in order to prevent generation of color irregularities.
In order to solve such problems, JP-B No. 8-3630 has proposed a method in which, upon applying and forming a photosensitive resin layer, a fluorine-based surfactant is added to the coating solution. With respect to the fluorine-based surfactant, a copolymer between acrylate or methacrylate having a fluoro aliphatic group that has 3 to 20 carbon atoms and fluorine atoms of not less than 40% by mass, with hydrogen atoms bonded to at least three carbon atoms at the end terminal being substituted by fluorine atoms; and poly(oxyalkylene) acrylate or poly(oxyalkylene) methacrylate, which contains acrylate or methacrylate units having the fluoro aliphatic group in a range of 40 to 70% by mass in the copolymer, is used. With respect to fluorine-based surfactants used in a number of examples, those in which the oxyalkylene of poly(oxyalkylene) (metha)acrylate is oxyethylene, oxytriethylene or oxytetramethylene are adopted, and most of them have a weight average molecular weight of approximately 15,000.
Some of the above-mentioned fluorine-based surfactants used in examples of JP-B No. 8-3630 make it possible to smooth the surface of the photosensitive resin layer. However, these are still insufficient in adhesive property to the substrate, and, in particular, fail to provide a sufficient adhesive property to the substrate upon carrying out a transferring process onto a glass substrate and a substrate bearing semiconductors. Moreover, this document does not disclose anything about smoothness on the thermoplastic resin layer.
Moreover, in recent years, there have been strong demands for a high-speed transferring property from the viewpoint of cost reduction, and in the case when certain irregularities exist on a substrate to be transferred, upon carrying out the high-speed transferring process of a very thin photopolymerizable layer thereon, a problem is raised in which bubbles and the like are included between the photopolymerizable layer and the substrate to cause a defective transferring process.
For example, upon producing a multi-color image such as a color-filter forming process, this problem occurs when the second color photosensitive resin layer is formed on the first color pixel. Further, in the case when, upon producing a printed substrate and the like, fine scratches and dents exist on a copper surface of a copper-clad laminate due to a surface smoothing process, this problem occurs when a dry film resist layer is transferred thereon.
Japanese Patent Application Laid-Open (JP-A) No. 63-309946 has disclosed the fact that since fine irregularities on a permanent support or particles of fine contaminant and dusts on the permanent support or the transferring layer or both of these interfere with sufficient adhesion of the transferring layer to the permanent support, a detective transferring tends to occur, and the application of a temporary support having a compressing property in order to prevent this undesired defective adhesion. Although this method is certainly effective, it is not sufficient in transferring a non-adhesive photosensitive resin layer onto a permanent support having irregularities that have the similar thickness as the thickness of the layer at room temperature, without causing bubbles thereon.
Japanese Patent No. 2794242 has disclosed an image forming material in which an alkali-soluble thermoplastic resin layer, an intermediate layer and a photosensitive resin layer are formed on a temporary support in this order. However, in the case when, in order to increase the transferring speed, a flexible material is used for the resin to form the alkali-soluble thermoplastic resin layer or when a great amount of plasticizer is added, a phenomenon (hereinafter, referred to as reticulation) occurs in which fine wrinkles are generated on the intermediate layer upon forming the alkali-soluble thermoplastic resin layer and the intermediate layer on the temporary support, causing irregularities to remain on the surface. The reticulation causes a problem in which smoothness in the photosensitive resin layer applied onto the intermediate layer is interrupted. For this reason, it has been difficult to achieve both of the high-speed transferring property and the prevention of reticulation. Moreover, the developing process tends to fail to sufficiently dissolve the plasticizer in the developer, with the result that troubles in transporting solution, such as pipe clogging in the developing vessel, tend to occur frequently.